Subject: 'alim religious warrior
Culture: Achinese
Setting: Dutch war, Aceh 1873-1904
1. Kuala Lumpur rencong
Many commenters claim that smaller rencong knives like this were concealed in clothing, but I'm unconvinced. The odd hilt shape makes concealment difficult and risks snagging on fabric. Aceh had other small knives of more streamlined shape that would've been much better both to hide and draw.
2. Horse head rencong
Figural art isn't consistent with 19th century Achinese art sensibilities, and naturalistic art isn't consistent with Indonesian art generally. So the horsehead hilt here isn't original. Without any provenance, guessing how it became associated with a rencong blade and scabbard isn't productive. The scabbard is hollowed from a single piece of wood, a technique of scabbard making associated with peninsular Malays (Steel and Magic 2020px).
